Network protectors are used in electricity distribution systems. A network protector automatically connects and disconnects an associated power transformer from a network when power starts flowing in a reverse direction. Typically, the network protector is set to close when the voltage difference and phase angle are such that the transformer will supply power to a secondary grid. Conversely the network protector is set to open when the voltage difference and phasing angle is such that the secondary grid would back-feed through the transformer and supply power to the primary circuit.
Network protectors may be located in a specific NEMA environment, such as underground vaults. Network protectors that are located in underground vaults may be exposed to moisture, sewage, dirt, small animals, and other contaminants. To protect the stability and dependency of the secondary grid, the network protector should be able to withstand a harsh environment. To provide protection against a harsh environment, the network protectors are often housed in enclosures made of corrosion resistant epoxy coated steel or corrosion resistant stainless steel.